Wounds are generally categorized as either acute injuries such as trauma, surgical wounds, burns, abrasions, avulsions, or as chronic wounds such as diabetic ulcers, venous stasis ulcers, and chronically infected wounds. In either instance, wounds require an appropriate wound dressing for protection from further injury, foreign debris, and infection and for enhancement of the healing process. There is a well documented need for a better wound dressing that is capable of addressing the multiple facets of wounds, especially chronic wounds, and ensuring that patient comfort is maintained. There is also an unmet need for more user friendly wound dressings.
Desirable characteristics of effective wound dressings vary depending upon the type of wound to be treated but generally include that they are moist, sterile, able to manage wound exudates, able to conform to the wound topography (be flexible), and able to adhere to the surrounding tissue but also be easily removed to prevent re-injury of the wound bed. Additionally, an effective wound dressing should provide mitigation for infection or the likelihood of infection.
The potential for developing a wound infection depends on many factors such as the cause of injury in acute wounds, migration of bacteria from intact skin to compromised skin in surgical wounds, and infections that develop from the lack of an effective barrier. It is thought that unresolved infections are the primary culprit for wounds that transition from acute to chronic.
When the integrity and protective function of the skin is breached, different cells migrate to the wound, starting the inflammatory response for healing the wound. This inflammatory response can be visualized at the macro level by redness, pain, and swelling. Infections from bacteria, viruses, and fungi are known to delay the wound healing process because the body first must fight the infection before it can heal itself. The risk of infection depends on the patient's condition as well as extrinsic factors such as post-operative/wound care, environment, and treatment. Since infection stems from many sources, is hard to predict the occurrence of an infection and the type of infection, which confounds the treatment options and methods. The prevention of wound infection is a primary management objective for healthcare practitioners.
In order to reduce infection and the possibility of infection, a wound dressing can include antimicrobial agents. One agent that has been used successfully is silver. Silver works as an antimicrobial agent through a number of pathways. It acts on the cell wall to inhibit cell wall replication. Silver can also inactivate the cellular respiratory chain and block the energy supply of cells, or directly act on nucleic acids such as RNA and DNA. Without those functions, the bacterium is inhibited from replication and effectively killed. This method of action is also ideal for preventing strong strains of bacteria with resistance. Because silver affects so many different functions of the microbial cell, it is nonselective, resulting in antimicrobial activity against a broad spectrum of medically relevant microorganisms including bacteria (both gram positive and gram negative strains), fungi, and yeasts. Silver is also more efficient than traditional antibiotics because it is extremely active in small quantities. For certain bacteria, as little as one part per billion of silver may be effective in preventing cell growth.
Hydrogel dressings have been proven effective in facilitating the repair of pressure ulcers, diabetic ulcers, and burns in addition to acute wounds such as cuts, scrapes and surgical wounds. A hydrogel is a network of polymer chains that are dispersed in water. The water content in a hydrogel can be adjusted within a wide range so they can be moist, if desired, or more absorbent and able to handle wound exudates. Hydrogels can possess a degree of flexibility that is very similar to natural tissue. Active agents can be directly and easily loaded into the hydrogel matrix. In addition, hydrogels do not require pre-wetting and have supplanted saline moistened gauze for many applications. Hydrogels can adhere to the intact skin without sticking directly to the injury or wound bed. A hydrogel based wound dressing can be transparent, offering the additional advantage of allowing direct visualization of the wound bed. Hydrogels can be preformed or in situ formed. Application of a composition that forms a hydrogel in situ on the wound site offers a significant advantage over a preformed hydrogel because it results in a dressing that conforms to the surface of the wound and may be used to help quantify the healing rate of the wound based upon volumetric comparison of the dressing.